Lazav is a shapechanger like no other, hidden in twighlight - leaving people to know very little of his origins. This powerful planeswalker not only gathered what was left of the guildmembers of Dimir, but he leads them in total secrecy.  Going as far as rebuilding the Duskmantle in a obscure place unbeknown to others. Protecting it and it's followers inside with powerful memory wards. The only thing that worries us, is if he performs his tasks under his own volition, or is he ordered by an ever greater power?

Well that power is you! With this deck you have control. You draw cards when you want, you choose what cards you draw next, and most of all - you choose what your opponent plays, and when to play them - if at all. Then even when your opponent thinks they can play what they want, send out Lazav's strongest assassin Etrata to finish the job - or was it Lasav themself, that dealt the final blow?

Main Deck Description, Tips, & Tricks
Surveil: Almost all the cards in the deck have this ability, because it's an amazing ability. Use it to get to Etrata, the Silencer as fast as possible so she can start building those hit counters. Use it to always have a counter, or land in your hand. Use it to fill the graveyard for Lazav, the Multifarious to shapeshift into (like Etrata, the Silencer).
Spell Pierce: Honestly you could switch this out for Quench, Negate, or Syncopate - whichever is your fancy.
Essence Capture: Counters a creature spell for 2 which is really good, but the reason I personally love this counter so much is the +1/+1 counter. That counter pulled through for me, more times than I can count.
Dimir Spybug: Very simple, this card works off almost the rest of your entire deck. The surveil ability. So while you are choosing what cards you're going to get and when you want to get them. It is a strong flier that just keeps getting stronger because of it. He could win you the game on this ability alone if the opponent isn't careful.
House Guildmage: Combat about to start? Tap. Oh you were about to use that tap ability? Tap. Oh you were going to kill my Dimir Spybug because he is a 4/4 flier? Surveil. Not the card you want to be picking up all the time, but pulls you through some kinks when it does come up. You can just feel your opponents annoyance when you tap their creature, right before exiling it with Etrata, the Silencer. If it ends up in the graveyard, that's just another thing for Lazav, the Multifarious to turn into - uh oh.
Lazav, the Multifarious: This is where it get's real. Any creature that is in your graveyard. You can make Lazav, the Multifarious that creature. Meaning you can have two Etrata, the Silencer's on the field at once, that's 8 Etrata, the Silencer's in your deck. You can have guildmage any time you want, or another Darkblade Agent. I wonder what they will be next!?
Thought Erasure: Surveil. Then make your opponent discard a card. You're opponent can't thwart your plans if they don't have a hand.
Sinister Sabotage: So let's theorize they do cast something. Well, you surveil, and send whatever nasty they tried to cast straight to the graveyard.
Darkblade Agent: In a surveil deck, you can just consider this a 2/3 for 3 that not only has deathtouch, but lets you draw cards when it deals combat damage.
Disinformation Campaign: I get to draw, you get to discard. Then when I surveil I get to pick this up and we can do it all over again! With Thought Erasure you'll be the only one with a hand and no one likes top decking. Well except you, because surveil.
Theif of Sanity: This is a fun, but confusing card, so let me explain it to you. When he deals combat damage to a player, you see that players top 3 cards.  Then you pick one of them, and can cast that card whenever you want and have the mana available (which colors don't apply). The other cards get sent to the graveyard, and if Thief of Sanity is destroyed or exiled they still don't get their card back. So it's win-win. Lazav, the Multifarious also can become this.
Magistrate's Scepter: You know. I didn't know how good this card was till I pulled it in a draft pack. This card is great and it just does it's own thing. If you have the 4 mana to spend (which your spells are realatively cheap so in the mid to late game, you possibly will be putting a counter on this per turn), spend the mana and get an extra turn after you make 3 counters. On paper that sounds long - in game it doesn't feel as long, and your opponent tends to even forget it's. Taking an extra turn is a BIG power boost in MTG, and with this deck makes it all the better.
Etrata, the Silencer: The butter to your Lazav, the Multifarious bread. If your opponent didn't already surrender because of how annoying your deck was before playing this card. When you attack with this card and they see the ability, they may just surrender then too. Especially if they destroy it, and you have Lazav, the Multifarious turn into it anyways. Using this card is simple. Attack, choose a creature your opponent controls, exile that creature, and that exiled creature gets a hit counter. When you have made 3 hit counters you win.
Hostage Taker: It's a Theif of Sanity, but for the creatures your opponent has on the field. This deck keeps getting more Dimir when you are literally taking their creatures hostage and bending their minds to your will. Simple play Hostage Taker, pick a creature your opponent controls, exile that creature, and then you can play that creature yourself for it's converted mana cost. Only problem, if Hostage Taker dies they get their creature back, and any effects it has that activate when it "enters the battlefield" will happen again - so be careful and protect your pirate.
The Eldest Reborn: It's the ultimate control card for 5 mana. When you play it, your opponent sacrifices a creature. The next turn they discard a card. The next turn you bring back whatever is the most powerful thing in the graveyards at the time to your side of the field and win the game.  With Magistrate's Scepter suddenly this happens a lot faster.

Sideboard Description, Tips, and Tricks
Duress: If your not discard the opponents hand fast enough. This card really helps against weenie decks that can take off really fast. You can throw away some early game threats from the door and severly crippling them into the mid/late where you take full control.
Unmoored Ego: Honestly what blue/black decks are not running Ego in their sideboard, and the only reason is Teferi. Work's great if you are against any deck that is based around one or two cards, like Dovin, or Nicol Bolas, or Kaya, or any other planeswaker based deck.
Sleep: Remember when you first started playing, and you always used the "Jungle Secrets" merfolk deck. Yeah. This card is still broken. For 4 mana you put to Sleep your opponents whole field and they stay tapped for a whole extra turn. Shuts down aggro decks.
Ritual of Soot: Again to shut down aggro decks, but also works perfectly well for weenie, and token decks.
Tome of the Guildpact: May take a while to bring out, but if you are finding into the late game you have no cards even with Darkblade Agent, and Disinformation Campaign. This will deffiently get you the cards you need fast, almost all the cards in your deck are multcolored.
Mass Manipulation: Did that 3 colored deck pull you into the late game before finally beating you? Well then swing back with these in your deck to turn the whole field they setup on them instead.

Disclaimer
I got inspiration for this deck when I was trying to choose a guild bundle to buy on MTGA store, and wanted a deck that was truly inspired by Lazav, their story, and still be competitive in Ranked and Casual play. I hope you have as much fun with this deck as I have. It is viable to use to Mythic in MTGA.